Norton on Fire!!!!

Joined
Mar 3, 2007
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6
Not really, but that's what the neighbors think with the amount of smoke my bike pumps out :? What started out as an engine rebuild with some fancy "new" Amals has turned into a nasty headache. I've bored my standard 850 to .020 and put in JRC pistons and rings. I'm also using a fire ring head gasket. A local shop replaced my valve guides, and the head needed nothing else. After I get it all back together the bike billows white smoke, plugs are completely covered with oil. So I tear the bike down to the base again, this time being EXTRA careful to line up the piston ring gaps just like the book says, put it all back together, being EXTRA careful tourqing down the head, and of course the smoke is still there, billowing away. What gives!? No way a leaking head gasket could cause this and I'm just scratching my head. I thought new pistons and rings would eliminate the smoke, not make it worse! Please someone give me some advice!
 
Joined
Apr 7, 2004
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1,691
Did you use oil when you put the new rings in? They are to be fitted dry. Trapped oil in behind the rings will stay there and burn to a nice Carmel.Just a few drops on the piston skirts will do the trick. How large was your pre-prime to the engine cases? Just 200 cc will do the trick . Does the motor breath ? that is when someone kicks it over with your ear to the end of the breather hose you should hear air passing.
 
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Oct 19, 2005
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Did you check the ring gaps prior to assembly? Also did you check that the piston tings are the correct way up? Both of these items could cause problems.
 
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May 19, 2006
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You can narrow things down a bit by blanking off the oil feed to the head temporarily to see if things improve. Have the rocker spindles been replaced the right way round ?

The guides themselves could be suspect. You wouldn't be the first person to be caught out by badly fitted or undersized guides installed by professionals. The oil can just as easily be drawn down the outside of the inlet valve guides if they're a sloppy fit in the head.
 
Joined
Mar 3, 2007
Messages
6
I've checked...

I'll look at all of those things--just dont want to have to tear the engine down again. I didnt use very much oil at all on the pistons, just a swipe with of the finger. As far as the head, the shop said they replaced the valve guides, and everything looked fine. But for all I know they just took me for a chump and charged me 80 bucks for nothing....not that I'm cynical 8) . I didn't think the rings had a "top" or "bottom" position since the Norton manual says nothing about that. Perhaps the JRC rings are not made as Mr. Norton intended. I figure oil must be entering the combustion chamber from somewhere though--and I mean LOTS. This is no wispy plume, but rather a James Bond-esque smoke screen.
 
Joined
Mar 3, 2007
Messages
6
not again...

Well I tore my engine down a 3rd time and the rings are not labeled "top". So unless there is something I'm missing I guess it is the head.... Hope no one else is as frustrated with their Commando as I am. :x
 
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Oct 19, 2005
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Joel, the rings may not be labeled 'Top' but often they are in fact chamfered and do need to go the correct way up, sometimes they have a number stamped on top of the ring. Normally there are instructions in the box that the rings come in. Good luck.
 
Joined
Mar 3, 2007
Messages
6
solved

Turns out it was my rings. In between the oil scraper rings is a bang that is marked on the ends with red and green paint (JRC version). I had overlapped the ends so this caused the scraper rings to pull into the piston rather than push out so oil was being sucked past those rings, the compression rings, and into the combustion chamber. So now the bike runs and doesn't smoke. Problem solved. Thanks to everyone who replied!
 
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